False decrease of HBsAg S/CO values in serum with high-concentration rheumatoid factors

•False HBsAg-positive results given by one-step ELISA were present in RF-positive sera.•Dilution caused elevation of false HBsAg-positive rate in serum with high-level RF.•High-level RF caused significant decreases of S/CO. Values of HBsAg.

ObjectivesTo investigate whether high-concentration RFs cause false decrease of S/CO values of serum HBsAg.Design and methodsSerum HBsAg was determined in 100 RF-positive sera using one-step ELISA. Twenty-three HBsAg-negative sera with high-concentration RFs were selected randomly to perform dilution with mixed normal sera. Serum models consisting of HBsAg and high-concentration RFs were made by blending high-concentration RFs and HBsAg-positive sera at the ratio of 9:1.ResultsIn the 23 samples, one-step ELISA showed that HBsAg-positive rate was 69.57% at dilution of 1:2, 60.87% at dilution of 1:4 and 40.00% at dilution of 1:8, whereas two-step ELISA showed that it was 100% without any dilution. Thirty serum models were made and divided into six groups. Median S/CO value of HBsAg was 3.00 in control, whereas it ranged from 0.13 to 1.78 in the six groups.ConclusionsHigh-concentration RFs cause false decrease of S/CO values of HBsAg using one-step ELISA.

Graphical abstractIn this study, RF was demonstrated to have the ability to influence the result of serum HBsAg provided by one-step ELISA, furthermore, the influence depends on the concentration of RF. High concentration RF leads to significant decreases of HBsAg S/CO values and occurrence of false HBsAg-negative result. The following Fig. introduced the possible mechanism which high concentration RF leads to significant decreases of HBsAg S/CO values.Figure optionsDownload full-size imageDownload as PowerPoint slideFig. The schema shows that high concentration RF causes false decrease of HBsAg S/CO values given by one-step ELISA.